Engine balance



Dec. 27, 1927.

1,654,515 w. R. TOMPKINS ENGINE BALANCE Filed May 13, 1925 2 Sheets-Sheet 1 WITNESSFS 16 INVENTOR 7 7: .7 l1r/I/r (149.

ATTORNEYS Patented Dec. 27, 1927.

UNITED STATES PATENT A "owl -cs.

WILLIAMRQY TOMPKINS, or .RAivx'IN, iLLINoIs.

ENGINE: BALANCE.

Application filed 'May 13, 1 925. I Serial No. 30,059.

' toica use vibrationsi'in a four cylinder: engine.

HA further object of lthe invention :is it-he provision 'of a balancing device which 31s adapted to bev actuated by the iro'tationof the crankshaft of areciprocating engine to set up forces equal to andactingin opposition to thefor'ces whichi'tend to cause thevibrations of the engineduring' each complete rotation of the crankshaft.

Other objects and advantages of the invention will be ppal'ent from the followin description,: considered in: conjunction with the accompanying drawings, in which Figure 1 is'a side elevation of a four cylinder reciprocating engine equipped with a balancing device embodying the invention, portions of theengine block" being :broken away to show the position of the device' with respect to the crank-shaft andv primary reciprocating. partsof the "engine.

TFigure 2-is aside elevation of a portioirof the crank shaft, showing :the deviceapplied thereto,

Figure 3 is Y a transverse vertical section through: the crankshaft showing" the balancing device in elevation and *showing the crank armsin a vertical plane; and

Figure 4: is a'vi-ew'similar toFigureB,

showing the crank :arins in a horizontal plane.

In the drawings, I showthe device applied to the. crank shaft of a tour cylinderxinternal combustion engine 'operating on 1 a four stroke cycle. In an engine of the type illustrated in the drawing, each complete rotation of the crank shaft ordinarily :is attended by two complete secondary vibrations of the engine. In anwengine of the type justdescribedthe cranks are positioned 180 apart and the forces'whiclr are setup when the crank shaft is rotatedand'whi'rh tend to cause the twosecondaryvibrations during each'complete rotation of the crank shaft act substantially" along a linerparallel to the direction of reciprocation ofthe pistons of the engine such forces resulting from thevshifting of the' center of gravity of the combined primary reciprocating 3 parts and the crankshaft -of the en'gi-ne as thecrank shaft rotates. In an engine' of the type;-il-- lustrated in' Figure 1, this shifting of the center i of gravity of the :comb'ined' primary reciprocating "parts oi"- the engine takes place along a {substantially vertical line during each" rotation of the cr'ank shaft.

WIncarry'ing out the "inventi'om I prefer to make use of a pairof identical canis' -l whichfare fiad rigidly to the crank shafts of the :enginey prefer-ably at the opposite-ends of lithe ma'in center bearing. 3 "for the crank shaft. The-cams l'may be formedintegrally with the I crank' shaft and have the forni of plates which'are' elliptical' in outline; the major axis oi -each oam comprising two relatively long lines of equal 1 length extending radiallyfromthexaxis of rotation of the crank shaft 'inthe' planebf the crank arms of the c'rank shaft vvhile the minor axis of each cam 1 comprises two shorter equal lines extending radially from the axis of -ro--' tation of the crank: shaftin ap lane' whi'ch extends at right angles'to [the plane of the crankiarinsof the crankshaft.

:This anrangement contemplates the turning 'o flthe cams with thecrank shaft at' the samespe'ed as "the crank shaft and the forming 0f the TCQJIHS'TWllJh regular-1y c'ur-ved pe riplreral surfaces. 1 If: provision should be made'itorotatethe canis'at'aspeedtwice that of the-"crank shaft,-each earn "would-be formed withi only one long radius and one short. radius which will be :in line with the relatively along radius 1 whereas each cam would'hbe formed with four relatively long radii of equal length and four shorter radii' ofequali length alternating with the' r'efllatively long radii if provision should be made toro'tate the canis at one-halt thespeed of rotation oi fthe crank shaft.

, Asweight 4 :is disposed belo'wthe "main" centrally 'of' 'the latter. .7 The-respective 'roll-' ers 8 have theirperipheral surfaces in rolling contact with theperipheral surfaces-0f the corresponding cams 1. Hanger bars 10 are supported at their upper ends on horizontal pivot elements 11 which are carried by lugs 12 or other attaching members which are fast to the engine block. Pairs of the hanger bars 10 depend on opposite sides of the main bearing 3 for the crank shaft and on opposite sides of the weight 1. The lower end portions of these pairs of hanger bars support horizontal pivot elements 13 which are parallel with each other, with the pivot element 6 and with the axis of rotation of the crank shaft. Bell-cranks 1 1- are fulcrumed on the pivot elements 13 between the hanger bars 10 of the respective pairs of hanger bars. These bell cranks l i have arms 14 overlapping at their extremities and pivotally attached to each other and to the lower portion of the weight 4 by a horizontal pivot element 15 which is parallel to the axis of rotation of the crank shaft. The other arms of the bellcranks are indicated at 14" and are provided adjacent to their extremities with openings 15 through which a rod 11') extends loosely. Similar expansion springs 17 are disposed on the end portions of the rod 16 at the outer sides of the arms 1 t of the bell-cranks. Each expansion spring .17 reacts at its inner end against the adjacent arm 14-" of the adjacent bell-crank and at its outer end against a stop washer 1.8 which is retained in adjusted position on the rod 16 by means of a nut 19 which is in threaded engagement with the rod 16.

From the foregoing description of the various parts of the device, the operation thereof may be readily understood; The springs 17 will act on the bell-cranks to hold the rollers 8 continuously in rolling contact with the peripheral surfaces of the cams 1. The weight supporting arm 5 is relatively long and since the extent of vertical movement of the weight during a complete rotation of the crank shaft is slight, the weight will move during a complete rotation of the crank shaft in a path which is substantially in line with the direction of reciprocation of the pistons 20 of the engine 21 which is shown in the drawings as being equipped with the invention.

Only three of the pistons 20 of the engine 21 are shown in Figure 1 of the drawing but it will be understood that the engine illustrated in Figure 1 has four pistons and that each of these pistons is connected with the crank shaft by means of a connecting rod 22. The weight will move in response to the action of the cams 1 on the rollers 8 as the crank shaft rotates in a path which is substantially in line with the line along which forces tending to cause secondary vibrations of the engine are exerted. In

other words, the weight will shift as the crank shaft rotates along a path which is substantially in line with the path along which the center of gravity-of the combined reciprocating parts and crank shaft of the engine shifts as the crank shaft rotates. However, the direction of movement of'the weight is opposite to the direction of shifting of the center of gravity of the combined reciprocating parts and crank shaft of the engine so that the forces which tend to cause secondary vibrations of the engine will be balanced and neutralized by forces set up by the shifting of the weight. The engine therefore will operate smoothly and without the usual secondary vibrations when a prac-' tical embodiment of the invention, such as has been described in the foregoing, is applied to the engine. Y

While l have shown the invention asv applied to a four cylinder internal combustion engine in which the line of shifting of the center of gravity of the combined reciprocating parts and crank shaft is ina vertical plane, .it will be manifest that the invention is equally applicable to other reciprocating machinery, as for example to an eight cylinder engine of the V type in which the direction of shifting of gravity of the reciprocating parts and of the crank shaft is in a horizontal plane, the invention then being embodied in a construction which supports the weight 1%. for shifting substantially in a horizontal plane and of coursein opposition to the direction of shifting of the center of gravity. of the reciprocating parts and crank shaft of the eight cylinder engine.-

It will be understood of course that the cams and the weight need not be applied to the crank shaft at the center hearing but may be distributed along the crank shaft equi-distant from a vertical line passing through the crank shaft at the point at which the line of shifting of the center of gravity of the reciprocating parts and the crank shaft intersect the crank shaft. The forces which tend to cause the secondary vibrations of the engine vary as the crank shaft is rotated. The construction which the invention provides as illustrated in the drawings and as hereinbefore described and consisting of the cams in rolling contact with the rollers which are carried by thespring actuated weight sets up forces whichvary directly as the forces that tend to cause the secondary vibrations vary and therefore the balancing action of the device'is uniform throughout the complete rotation of the. crank shaft. 7

Obviously, my invention is susceptible of embodiment in forms other than "that illustrated in the accompanying drawings and I therefore consider as my own all such modifications and adaptations of the form of the device herein described as fairly fall within the scope of the appended claims.

I claim s 1. A device for balancing the secondary forces of a reciprocating'engine, comprising a cam carried by the crankshaft of the engine and having a regularly curved pe opposite the primary reciprocating parts of the engine so that the weight can move along a path substantially in line with the line along which the center of gravity of the reciprocating parts shifts as the crank shaft is rotated, a roller supported by said Weight for rotating about an axis parallel to the axis of rotation of the crank shaft and in position to have rolling contact with the peripheral surface of said cam, a bell crank fulcrumed adjacent to said weight and pivotally attached at one end of said weight, spring means acting on said bell crank to cause said weight to be held continuously in position to cause rolling contact of said roller with the peripheral surface of said cam, and means for adjusting the pressure on said spring.

2. A device for balancing the secondary forces in an internal combustion engine operating on the four stroke cycle, comprising a pair of cams carried by the crank shaft equi-distant from the intersection of the crank shaft with the line along which the center of gravity of the combined reciproeating parts of the engine shift as the crank shaft is rotated, each of said cams being elliptical in contour and having opposed relatively long radii of equal length lying in the plane of the crank arms of the crank shaft and having opposed shorter radii of equal length lying in planes at right angles to'the plane of the relatively long radii, a pair of bell-cranks fulcrumed below the level of the crank shaft to swing about axes parallel to the axis of rotation of the crank shaft, said bell-cranks having arms overlapping below the axis of rotation of the crank shaft, a weight pivotally attached to said lapped portions of said arms of the bellcranks and supported for movement toward and away from the axis of rotation of the crank shaft along a path substantially in line with that along which the center of gravity of the combined reciprocating parts of the engine shift as the crank shaft is rotated, rollers supported by the weight at opposite sides thereof and respectively in rolling contact with the peripheral surfaces of the corresponding cams, a rod extending loosely through openings in the ends of the remaining arms of said bell-cranks, and oppositely acting springs on the ends of said rod acting on said bell-cranks to tend to force said weight continuously toward the axis of rotation of the crank shaft, as and for the purpose described.

WILLIAM ROY ToMPKINs. 

